M4 Rear Input Problem

[Resonant Alien]

The rear input on my M4 is not working very well - I get inconsistent volume - the volume flucuates up and down randomly. The front input works just fine. Do the front an rear inputs used different tubes? if so, maybe this is a problem with the tube on the rear input? There is no crackling like you normally get with a bad tube though.

Thanks,

 

[guitarslinger]

if the front input works fine, then you have a bad wire or connection from the rear jack to the front jack. I'm guess they are just linked in parallel.

 

[Resonant Alien]

Thanks. I think I'll de-rack tonight and take a peek inside - maybe it's something simple and obvious like that, and I can take care it myself without shipping back to EG